April in Sarnia averages a daily high of 12.8°C with nights around 3°C. Expect roughly 12.4 wet days totalling 77.5mm. Demanding conditions — pack for it and plan indoor options.
Across the year, the best time to visit Sarnia is May–September.
Based on PORT HURON, MI US (1.3km), 1995–2024. 30 years of April data.